London's Royal Academy, which is currently mounting an exhibition of Ai's work, is encouraging supporters to fill a BMW in its courtyard with Lego bricks for Ai.

Other galleries have also taken up collections, including the Brooklyn Museum in New York, Berlin's Martin-Gropius-Bau and Australia's National Gallery of Victoria, where an exhibition of Ai's new work is due to open in December.

Lego declined to comment on the specific case, but said it refrained "from actively engaging in or endorsing the use of Lego bricks in projects or contexts of a political agenda."

It said that "anyone can purchase Lego bricks in toy stores or in other ways and use them for any purpose they desire."

Passerby Lena Lauschuss prepares to drop Lego pieces into a car that is being used as a collection point for donations to Ai Wei Wei on Oct. 30, 2015 in Berlin.Sean Gallup / Getty Images

The company is eager to avoid artistic controversies like the 1996 incident in which provocative Polish artist Zbigniew Libera created a concentration camp toy set with its blocks. Since then, his death-camp toys have been shown in museums and galleries around the world.

Lego said then that it had given some of its building blocks to Libera when he asked for a donation, but would have refused had it known what he planned to make with them.